When Monica Osagie got low marks in a course for her master's degree, she says the professor gave her two options: Sleep with him, or fail the class.

Faced with this stark choice, Osagie says she knew no one would believe her word against the lecturer's, so she recorded one of their conversations using a cell phone app.

The audio recording was leaked online and went viral on social media. Osagie says she did not leak it but had submitted it to university authorities before it surfaced online.

The student's allegations, coming amid the conversations around the global #Metoo movement, have now sparked a nationwide conversation in Nigeria about predatory sexual behavior on campuses and bolstered the notion that sexual harassment is a problem women the world over face almost every day.

In the recording, a man can be heard saying that if the student agreed to have sex with him five times, he would improve her grades.

"Is it not five we agreed? Our agreement is five," the man says on the tape.

Osagie replies, "Is it B that you want to give me or A? Why would it be five times you will knack me? Prof, you know what? Let me fail it. I can't do it five times."

Student speaks out

In her only interview since the audio was leaked online, Osagie, 23, told CNN she had developed a mentor-mentee relationship with the professor after she helped him edit his book.

But the relationship soon made her uncomfortable because he started to make sexual advances towards her, she said.

"We actually edited the book together... Then, the next thing he told me was, 'Can you date me?' I was like, 'No.' He was like, 'Why?' I said, 'One, I don't date lecturers, and secondly, you are more matured than I am.'"

CNN hasn't been able to confirm the professor's age.

Osagie believes he deliberately gave her low marks so she would agree to sleep with him to raise them, she said.

"He kept calling me to ask if I was ready to accept his proposal. So, I decided to record our next conversation," she added.

CNN has listened to the recording but cannot independently verify it. But a spokesman for the Obafemi Awolowo University (OAU) in Osun State, south west Nigeria, has confirmed that the voice is that of Richard Akindele, an accounting professor at the university.

The university said in a statement posted on its website: "Professor Richard I. Akindele, of the department of management and accounting, is now established to be the lecturer in the controversial "marks for sex" audio recording. The female voice has also been identified as that of Miss Monica Osetobe Osagie, a postgraduate student on the Master of Business Administration Regular programme."

Terrible! Unfortunately, many universities don't have strong deterrents or punishment for abusers. Students should be encouraged to speak out when such things happen. There must be at least someone in the institution who can be trusted and confided in. Justice must be done. https://t.co/rpHyJmR8Oc

The university added that "it will continue to do everything legally and morally acceptable in pursuance of its avowed commitment to zero tolerance for sexual harassment, intimidation and, or coercion."

Akindele is yet to speak publicly and declined to comment to CNN.

"I have nothing to say until the university has concluded their investigation," he said.

Backlash on social media

Osagie says she has faced severe backlash since the university made her identity public when it released a statement.

"A guy came up to me at the bank and said, 'Is this not the girl who harassed a lecturer?' and he called me a prostitute. The security guard then had to push me away to go withdraw my money inside the bank," she said.

Osagie has also received abuse on social media and allegations that she tried to seduce the professor, she said.

Despite the criticism, Osagie says she has no regrets speaking about her experience. She hopes her case will give young women facing harassment on campuses the confidence to reject inappropriate advances from their lecturers, she said.

"I am actually happy I came out. I am helping many ladies that have gone through the same thing I have gone through, and most of them can't talk about it.

"They are scared of coming out in public. But I know it happens everywhere, not just in Nigeria. For me, speaking up will bring more women to speak and eradicate what is happening around young women and older men," Osagie told CNN.

"There is no work or ... education that is worth your dignity," she added. "I will keep saying that."

After the story broke in the media, Osagie faced a university panel investigating the allegations on the tape and is awaiting its findings so she can receive her certificate. There has been no suggestion that the findings will prevent her from receiving her degree.

Her lawyer, Abiola Akiyode-Afolabi, told CNN more victims have contacted her with allegations about the same professor since hearing about Osagie's case.

"We have ... a situation whereby people have promised to send to us affidavits ... where they can also give evidence against the professor," the lawyer said.

CNN has not been able to reach Akindele for comment about other accusers.

A spokesman for the university also told CNN the institution could not disclose whether other students had brought similar allegations against the professor.

"What is being investigated is the allegation leveled by the student against her lecturer. The university's council will make the final decision on the report the vice chancellor has submitted on the case," said Abiodun Olarewaju, a spokesman for OAU.

"This is because of the caliber of the lecturer involved," he added.

OAU hit by allegations of sexual harassment

Sexual exploitation of female students is a common practice in many universities in Nigeria, one lecturer told CNN.

"There is no doubt that this is something that happens frequently in our universities," said Remi Sonaiya, a former professor of French and linguistics at the OAU.

The practice thrives because students do not come forward with these allegations and also because they do not trust their institutions to handle such matters with discretion, she added.

"I handled a case where the female student reported to another lecturer. She did not come to me at first even though I was the head of the department," Sonaiya told CNN. "I felt bad she worried about who to tell, but I can't blame her. She didn't know who to trust.

"I hope this sends a signal that we can no longer tolerate these forms of assault on young women anymore," she added.

Osagie's case is not the first time OAU has been embroiled in a sexual harassment scandal.

A former student in January said in a now-deleted Facebook post that one of her lecturers caused her to drop out of school when he failed her after she refused to sleep with him, according to local media reports.

But it is not only happening in Nigerian universities. Makere University, Uganda's oldest university, last month suspended a male member of staff after a female student accused him of sexual harassment.

Ugandan local media also captured one of the school's male lecturers asking a female student for sex in exchange for marks. The man was later suspended by the university.

CNN has been unable to reach the two accused men for comment. A spokeswoman for Makerere University told CNN the university was investigating both cases.

"The university will issue an official notification when the investigations are concluded," Ritah Namisango told CNN.

The vice chancellor set up a committee in March after the allegations against the lecturer came to light to investigate the "increasing cases of sexual harassment" at the university. The committee will review and improve the institution's sexual harassment policy, she added.

A 2010 survey of college students and lecturers in Ghana and Tanzania universities found "sex-for-grades" was the most common form of harassment students faced on campuses.

Researchers interviewed 200 academics and policymakers and 200 students in the report, which highlights various forms of sexual harassment in the two countries.

"Interview data revealed heterosexual sexual harassment of women by men as a discursive and actual practice in all four case-study institutions," wrote Louise Morley, the lead researcher and professor of education at the University of Sussex, in the UK.

Some male lecturers in universities surveyed "consider it their right to demand sex with female students" in return for grades, researchers found.

Hashtag campaign reflects outrage

Since Osagie's recording went viral, many Nigerians have led calls for universities to do more to protect students from sexual harassment.

Any lecturer caught soliciting bribe for marks in Nigeria should be suspended for a full academic year.

Any lecturer caught soliciting sex for marks/good grades should be fired. RT if you support this.

"Any lecturer caught soliciting bribe for marks in Nigeria should be suspended for a full academic year. Any lecturer caught soliciting sex for marks/good grades should be fired. Retweet if you support this," Dipo Awojide tweeted.

Tweeting with the hashtag #StandingWithMonicaOsagie, many expressed anger at the university, which forced authorities to respond to her allegations.

If you’re a female in Nigeria and you’re not #StandingWithMonicaOsagie you are doing a disservice to your daughters and granddaughters - present or future! Fight abuse of power in schools and the workplace! No to sexual harassment!!!